The long-term objective of this research is to determine how molecular nitrogen can be reduced to ammonia catalytically at room temperature employing a transition metal complex and protons and electrons. The short-term objective is to investigate the chemistry of complexes containing molybdenum or tungsten in a relatively high oxidation state (4+,5+,6+) or rhenium (5+,6+,7+) that are relevant to dinitrogen reduction, especially monomeric complexes containing N2Hx and NHy ligands. Specific objectives for the next grant period include (i) an in depth study of monomeric complexes containing the MCp*Me3 fragment (M = Mo or W) and hydrazido(1-) or hydrazido(2-) ligands, or hydrazine, or ammonia; (ii) synthesis and study of related complexes containing the ReCp*Me3 core; and (iii) synthesis and study of other types of high oxidation state complexes to which dinitrogen, hydrazido, hydrazine, or ammonia ligands will bind to form complexes relevant to catalytic reduction of dinitrogen. In addition to synthesis we will focus on electrochemistry, 15N labelling and mechanistic studies, x-ray studies of proven intermediates in N2 reduction sequences, and the design of a catalytic homogeneous dinitrogen reduction system.